Linkage Plate

pmangelos · #1 (**permalink**) 03-06-2010, 01:23 PM

I see that someone had some linkage plates that go between the carbs on a 351 intake that the center bellcrank pivots on made up some time ago and was selling them. Does anyone have one that they want to sell, or are these still available thru the original source? Any help is appreciated, thanks.
Paul

Gun Doc · #2 (**permalink**) 05-24-2010, 04:09 PM

Paul,

I don't know if you ever got a response (PM maybe) to this question, but I too would be interested in a center linkage plate for a 351W.

Gun Doc

Rick Parker · #3 (**permalink**) 05-24-2010, 07:28 PM

I think Traindriver was the person who had those, haven't seen him post in quite a while.

bobcowan · #4 (**permalink**) 05-24-2010, 09:49 PM

You don't need anything fancy. All you want is a solid base to mount the bell crank to. Any flex or movement will mess up your balance.

My manifold has a drilled and threaded base in the center for the bell crank. But it was too low for good activation though out the operating range.

I made my own base out of some 1" octagonal alum bar stock. Drill a hole in each end. Drill and tap each hole. Put a stud in one end, and screw that into the boss on the manifold. Bolt the bell crank into the other hole. Nothing fancy, but it works. I also used a steel thread insert into each tapped hole for extra strength. One of the big tricks, though, is that the cuts must be perfectly square.

If you don't have the mounting boss on your manifold, I don't imagine it would be that big of a deal to drill and tap a hole dead center in the valley.

I also made my linkage arms out of 3/8" alum hex bar stock. Same thing Inglese sells, but a whole lot cheaper.

Rick Parker · #5 (**permalink**) 05-24-2010, 10:57 PM

What Bob said is correct, it is not difficult to create a tower to mount the bellcrank on, but it must be placed properly or you will never get your cabs to open equally. First of all assuming the fuel lines attach to the outside of your carbs(?). The following will then apply and can also be used on manifolds that already have the mounting tower cast as part of the manifold. Remove the carb mounting nuts (if you are using studs) for the 4 studs on the inside of the center 4 carb throats. Stretch 2 rubber band attached around the studs to form an "X" in the center of the manifold.The small diamond formed by the intersecting rubber bands is wher the hole is to be drilled to anchor the bellcrank tower. If you already have a tower cast in the manifold you will probably see the attaching pivot hole needs to be moved about 3/4". Design what you will carefully, your carb syncronization depends on it.

Gun Doc · #6 (**permalink**) 05-25-2010, 08:43 AM

It was Train Driver who made those...I remember now, because he has the same PE 351W as I. The problem with the 351W Weber set up (at least all the ones I have seen) is the manifold does not have a boss cast into it. I will need some sort of plate to make it work. I don't feel real comfortable drilling and tapping the manifold; at least not while it is on the engine...Too much chance the hole will not be squared.

This will take some thought...

Gun Doc

onefastmustang · #7 (**permalink**) 05-25-2010, 09:34 AM

It was indeed Traindriver. I have one of the plates I got from him. A nice piece of work. I remembering Rick asking me where I got the fancy plate. LOL. There was a very good reason why I got it too. Some of the other methods of linking the carbs don't actuate them in 100% sync. Traindriver designed the linkage setup that I have as a way to prevent that so all of the carbs are throttled up in sync. I didn't believe this until I got the carbs/manifold from the vendor I purchased it from and looked at their linkage setup. It was apparent that the left carbs were being opened a small percentage more than the right carbs. Installing this plate made that go away.

Blittleton · #8 (**permalink**) 05-25-2010, 09:41 AM

Gun Doc

I made this bracket for one of our Backdraft's

Give me a call if you need something like this
859-630-9099

Bill

pmangelos · #9 (**permalink**) 05-25-2010, 12:04 PM

Thanks all for the imput. I have been working on my own system using a tower off of the intake, however, I have been having a few issues. I assume that I should have throttle return springs (independent of the springs on the carbs themselves), but the effort to work the throttle cable already feels fairly stiff and is not a linear draw as the tension of the springs acting on the cam on the bottom of the carbs is stiff then gets easier. I will post pics of what I have done so far to get others imput as to wheter or not it will operate properly or if I have a fatal flaw in my plan. Thanks all.
Paul

onefastmustang · #10 (**permalink**) 05-25-2010, 12:17 PM

Paul

Would a picture of my implementation be useful at all? I may have some drawings that traindriver sent me somewhere as well.

pmangelos · #11 (**permalink**) 05-25-2010, 10:33 PM

onefastmustang, any info that you can pass along is appreciated. Here is a picture of my setup at this time. I would like to add throttle return springs to this and have been trying a variety of things, but I haven't found anything that really works well yet.

onefastmustang · #12 (**permalink**) 05-25-2010, 10:59 PM

I took som pictures. I'll send them over tomorrow. I don't use any kind of return springs. You look to be on the right path on your implementation.

bobcowan · #13 (**permalink**) 05-26-2010, 10:55 AM

Quote:

Originally Posted by pmangelos

onefastmustang, any info that you can pass along is appreciated. Here is a picture of my setup at this time. I would like to add throttle return springs to this and have been trying a variety of things, but I haven't found anything that really works well yet.

That would be pretty easy. Use a standard spring, attache one end to the stud where the throttle cable is attached, and the other end to the metal that the throttle cable is based on.

onefastmustang · #14 (**permalink**) 05-26-2010, 11:20 AM

Do you really need any return springs? The ones in the carb seem to be plenty to me..

onefastmustang · #15 (**permalink**) 05-27-2010, 08:02 PM

Paul.. PM me your email address and I will send you all of these pics.. they are too big for the gallery.

Caprimaniac · #16 (**permalink**) 05-31-2010, 03:55 AM

Quote:

Originally Posted by bobcowan

That would be pretty easy. Use a standard spring, attache one end to the stud where the throttle cable is attached, and the other end to the metal that the throttle cable is based on.

As I would put it myself.

Although I use a different setup: Srping from carburator stud to underside of the throttlewire end attachment.

Works very well.

Mak_seile · #17 (**permalink**) 12-16-2010, 04:56 AM

The FSM is not to clear with how the linkage is arranged. It also appears Im possibly missing a piece. I found the needed bushings at the auto parts store.

Looking at the FSM, it looks like there is a piece that connects the two link bars together and attaches to the wiper motor drive crank. The passenger link bar hole is larger than the driver link bar bushing hole. Ive gone thru the cowl and there is no piece in there.

Any one have a pic of the piece I might be missing and how the arms are arranged?

jhirasak · #18 (**permalink**) 03-29-2012, 09:32 AM

I have a 48IDA setup with the carbs oriented so the fuel inlets on the opposite banks are pointed away from each other. With this arrangement, the linkage provided has a single bar conntecting the passenger side carbs to the driver side carbs. The resulting linkage geometry appears to allow the drivers side carbs to open faster than the passenger side carbs during the idle transition phase, equal opening rates at half throttle, and slower rates near full throttle. Because of this geometry, I have had to set the linkage so that all carbs are pulling the same amount of air when the engine is running from 1700 to 2000 rpms in order to have a smooth engine response when changing from the idle/transition circuit to the main fuel/air circuit.

Is this a problem that has been experienced by others using a single bar linkage? Would the correct action be to install a center bellcrank to connect the two banks of carbs?

Rick Parker · #19 (**permalink**) 03-29-2012, 09:52 AM

I have not seen the connecting bar linkage you have used succesfully without changing the pivot arms on the carbs. If you are not using a rod down the center to control the carbs individually with different length connecting links then I think the center pull bellcrank setup will be more accurate and trouble free. If you go with the centerpull setup make sure the stand is equadistant from the cabs and that the connecting links are the exact same length AND parallel when installing the stand.

bobcowan · #20 (**permalink**) 03-29-2012, 11:32 AM

A cross bar linkage like that can work just as well as a center bell crank. Or just as poorly.

The trick is how they are mounted to the throttle shaft. Both ends of the bar MUST move through the exact same arc. Otherwise, one bank will open at a different rate than the other bank, it it will run bad right off idle, and get worse as the throttles open wider. With your synchrometer, make sure the air flow is exactly the same in all 8 bores at idle and higher rpm's as well. I balance mine at idle and 2,500rpm's.

As long as the throttle levers are exactly the same at both ends of the arm, it will work just fine.